Can't i initialized empty String array and pass in the value afterwards in Java?

I can't seems to find out what what is wrong with my codes? i can't开发者_开发百科 pass in non-empty String value into an empty String array?

String[] profiles = wifiPositioningServices.GetAllProfileData();

ArrayList<String[]> macAddresses = new ArrayList<String[]>();
String[] macAddressTemp=null;

    //store all profile data into a ArrayList of Profile objects
    for(int i=0; i<profiles.length; i++){
        String[] result = profiles[i].split(",");
        Profile profile = new Profile();
        profile.setProfileName(result[0]);
        profile.setOwner(result[1]);
        profile.setMap(result[2]);
        profile.setVisible(result[3]);
        boolean visible = Boolean.valueOf(result[3]);
        if(visible){
            //if visible is true, then add profile name and mac filters into arraylist 
            profileNames.add(result[0]);
            int cnt=0;
            for(int j=4; j<result.length; j++){
                profile.setMacFiltersList(result[j]);
                Log.e("Text:", result[j]);
                macAddressTemp[cnt] = result[j];
                ++cnt;
            }
            macAddresses.add(macAddressTemp);
        }
        profileList.add(profile);
    }

Java show a nullpointer exception at the line "macAddressTemp[cnt] = result[j];". I am sure that result[j] is not empty cause i was able to print it out via the log msg.

Use an ArrayList instead.

ArrayList<String> macAddressTemp = new ArrayList<String>(100); //check capacity
macAddressTemp.add(result[j]);

EDIT:

You changed your code wrong. This ArrayList<String[]> macAddresses = new ArrayList<String[]>(); is creating a List that contains arrays. You have to create a List that contains String. Check the code above.

The array macAddressTemp is null.

The NPE is thrown because macAddressTemp is null. You probably want to declare and initialize macAddressTemp inside of the outer loop.

You explicitly set it to null:

String[] macAddressTemp=null;

You need to allocate some space for the array, or use a collection.